Militants who have attacked the oil industry
for five months said they had no hand in the killing of the executive,
who worked for Texas oil services company Baker Hughes Inc. A diplomat
and oil industry source said it was more likely the slaying was linked
to a work-related dispute.

Baker Hughes spokesman Gene Shiels confirmed
that the victim, Ricky Wiginton, 51, worked as an operations manager for
a division of the company. His hometown was not immediately available.
The U.S. Embassy said it was investigating the report.

The executive was being chauffeured through
a violent area of the city when he was shot in the chest, an industry source
said. The gunman was apparently working in coordination with a car that
impeded escape.

In an e-mail, the Movement for the Emancipation
of the Niger Delta denied involvement. MEND has bombed oil facilities,
kidnapped foreign workers and recently begun using car bombs.

Its attacks have led multinational firms
to cut Nigerian oil exports by one-quarter.

The industry source said Baker Hughes
had pulled its staff out of Port Harcourt as a precaution.

A company spokesman would not comment.

Port Harcourt is the largest city in
the Niger River Delta, and several oil companies have large offices here.
The city suffers from sporadic outbreaks of gang violence, and several
deadly armed robberies have occurred recently.

Much of the violence stems from deep-seated
resentment among inhabitants of the region, many of whom feel cheated out
of the riches being pumped from their traditional lands.